ABSTRACT
Staphylococci are the most frequently isolated bacteria from blood. The prevalence of antibiotic resistance has dramatically increased. Real-time PCR offers rapid, accurate, and sensitive method to detect the presence of antimicrobial resistance. This study is mainly aimed to detect uethicillin [oxacillin] and vancomycin resistant staphylococci isolated from blood of patients with significant bacteremia in Assiut University Hospital using both real-time PCR and phenotypic agnostic methods. Sixty Staphylococcal isolates were included. These isolates were collected from positive blood culture bottles [BACTEC 9050 System] of patients with significant bacteremia in Assiut University Hospital. Identification of staphylococcal species was performed by subculture on Mannitol Salt Agar [MSA] and by Microscan system, while antibiotic sensitivity testing was performed by Microscan system, Epsilometer test [E- test], Disc diffusion [DD] method, Oxacillin Resistance Screening Agar Base [ORSAB] and by real-time PCR for mec A and van A genes. Seven S. aureus isolates and fifty three Coagulase-negative staphylococci [CoNS] were detected by both MSA and Microscan system. The most effective antibiotics for staphylococcal isolates were in order. Vancomycin, Linezolid, Synercid, Rifampicin, Chloramphenicol, Gentamycin, Tetracycline, Trimethoprim/Sulphamethoxazole, Clindamycin, Ofloxacin, Ciprofloxacin, Azithromycin and Erythromycin. Concerning methicillin resistance, Real-time PCR which is the gold standard method detected mecA gene in 57 isolates. Accordingly, sensitivity and specificity of E-test were 964% and 100% respectively, DD method showed 87.7% sensitivity and 100% specificity, ORSAB media showed 92.9% sensitivity and 100% specificity while Microscan showed 100.0% sensitivity and 100.0% specificity. Concerning vancomycin resistance, E-test which is the gold standard method detected vancomycin resistance in 6 staphylococcal isolates. Therefore, the DD method showed 66.7% sensitivity and 100.0% specificity while Microscan showed 83.3% sensitivity and 100.0% specificity. Real-time PCR detected van A gene in only one staphylococcal isolate. CoNS organisms are more implicating than S. aureus in bloodstream infections [BSIs]. About 95% of staphylococcal isolates were resistant to methicillin and 10% were resistant to vancomycin. Real-time PCR was more accurate and rapid method for detection of methicillin resistance than phenotypic methods and it could be considered a confirmatory method for detection of vancomycin resistance in staphylococcal isolates suspected to have the van A gene